Split furnace and tube support



Sept. 6, 1955 F. o. HESS ET AL 2,716,968

SPLIT FURNACE AND TUBE SUPPORT Original Filed April 23, 1947 3Sheets-Sheet l ATTORNEY l l l F. O. HESS ET AL SPLIT FURNACE AND TUBESUPPORT Sept. 6, 1955 Or a1 F Sept. 6, 1955 HESS ET AL 2,716,968

SPLIT FURNACE AND TUBE SUPPORT Original Filed April 25, 1947 3Sheets-Sheet 3 INVENTORSS fieoerv'; O, #2:: BY Im /w e/Luhe/ ATTORNEY2,716,968 Patented Sept. 6, 1955 SPLIT FURNACE AND TUBE SUPPORT Frederict1). Hess and Kurt W. Fleischer, Philadelphia, Pa., assignors to SelasCorporation of America, Philadelphia, Pa, a corporation of PennsylvaniaOriginal application April 23, 1947, Serial No. 743,358, now Patent No.2,606,536, dated August 12, 1952. Divided and this application December26, 1951, Serial No. 263,247

6 Claims. (Cl. 122-510) The present application is a division of ourcopending application Serial No. 743,358, filed April 23, 1947, nowPatent 2,606,53 6.

The genera. object of the present invention is to provide improved fluidheating apparatus of the general type commonly referred to as tubularfluid heaters, in which the fluid heated flows through a bank of spacedapart parallel tubes located in a heating chamber. The fluid passingthrough the tubes of such a heater may be a liquid, vapor or gas.

The invention is primarily devised and adapted for use in oil crackingand other processes in which the fluid flowing through the tubes isheated to temperatures varying from 1566" to 2200 F., although theinvention may be used in heating fluids to temperatures somewhat higherthan 2200" E, and to temperatures substantially lower than 1500 F. inthe preferred form of the present invention, the heat utilized isproduced by the combustion of a combustible mixture of air and gas bymeans of gas burners mounted in the refractory wall of the heatingchamber and heating portions of said wall to incandescence, so that muchof the heat liberated is radiated to the tubes from the heating wallsand from the burner flames and combustion gases, though some of the heatabsorbed by the fluid is transmitted to the tubes by convection heating.

An object of the invention is to provide a supporting frame or rack forthe parallel spaced apart tubes of the tube bank, which is well adaptedto withstand high operating temperatures and which includes readilyreplaceable bracket-like parts of ceramic material on which the tubesare directly supported and which are supported by water cooled metallicmembers. Another specific object of the invention is to provide a tubesupporting structure which has practically no tendency to varysignificantly in shape or form as the result of variations in itstemperature, so that it is well adapted for use when the tubes areformed of quartz connected at their ends by return bends also formed ofquartz, as is desirable in some cases. Such a tube structure does notexpand or contract to any significant extent as a result of changes inits temperature, and might be subjected to damaging strains bysubstantial changes in the form of dimensions of the tube supportingstructure.

The various features of novelty which characterize our invention arepointed out with particularity in the claims annexed to and forming apart of this specification. For a better understanding of the invention,however, its advantages, and specific objects attained with its use,reference should be had to the accompanying drawing and descriptivematter in which we have illustrated and described preferred embodimentsof the invention.

Of the drawings:

Fig. 1 is an elevation partly in section on the line 11 of Fig. 2;

Fig. 2 is an elevation partly broken away and in section on the line 2-2of Fig. 1; r

Fig. 3 is a plan partly broken away and in section on the line 33 ofFig. 1;

Fig. 4 is a vertical section through the tube bank taken on the line 44of Fig. 3;

Fig. 5 is a section on the line 5-5 of Fig. 4;

Fig. 6 is a section on the line 6-6 of Fig. 5;

Fig. 7 is a partial section on the line 7-7 of Fig. 6;

Fig, 8 is a vertical section taken similarly to Fig. 4 and illustratinga modification;

Fig. 9 is a section on the line 99 of Fig. 8; and

Fig. 10 is a partial section on the line Ill-10 of Fig. 8.

The preferred embodiment of the invention illustrated by Way of examplein the drawings, is a continuous tubular heater comprising a furnacestructure A enclosing a furnace chamber B. The latter is horizontallyelongated and is of a height which ordinarily, and as shown, isappreciably less than its length, and is of a width appreciably lessthan its height. The furnace is heated by burners C incorporated in theside walls of the furnace chamber. A plurality of horizontal, parallel,spaced apart tube sections E are arranged in a bank or stack Dcomprising two side by side vertical rows, centrally disposed in thefurnace chamber. The tube sections E are supported by a tube rack orframe comprising a row of vertical columns F between the two rows oftubes, and lateral brackets G carried by the columns at their oppositesides, and directly supporting the tube sections.

Ready access to the heating chamber when necessary or desirable forinspection, repairs or replacements, is made possible by forming thefurnace structure A in two generally similar separable sections,respectively located at opposite sides of a vertical separation planewhich passes approximately midway between the two side by side rows oftubes E. In the preferred construction shown, the right half portion ofthe furnace wall structure, as seen in Fig. 2, is mounted on a truck ormovable platform H having wheels I running on track rails J extendingtransversely to the length of the furnace beneath and to each side ofthe latter. The left half portion of the furnace wall structure ismounted on a platform I: having wheels 1' which also run on the rails I.As shown, the platform It and wheels 1' are like the platform H andwheels I, respectively, and the furnace portions respectively supportedon the platforms H and it are similar in construction. Each of saidfurnace portions comprises refractory material forming one side Wal andhalf of the top and bottom walls of the furnace chamber and half of eachend wall of the furnace chamber B, and a metallic casing part K andmetallic buckstays L at the outer side of the casing structure andbraces LA, all arranged to give suitable mechanical strength andrigidity to each half furnace part, and to anchor it on thecorresponding platform H or 12.

Advantageously, and as shown, the burners C are of a type adapted toburn a combustible mixture of air and gas. In the form shown, theburners comprise blocks of ceramic material incorporated in the furnacechamber side walls and each formed with a central longitudinal passage Cterminating at its inner end in a shallow cup shaped combustion space CThe latter receives a combustible mixture through the passage C, andpasses gaseous products of combustion into the furnace chamber B proper,and its concave wall radiates heat into the furnace chamber. Each ofsaid burner passages C is connected at the outer side of the furnacewall, preferably through an individually regulable pipe branch 0', .to afuel and air supply piping system 0 secured to the corresponding side ofthe furnace wall. The piping systems 0 each customarily includes variousregulating and control valves including a throttling valve P in each ofthe branches 0'. Each piping system 0 is ordinarily connected by aflexible pipe connection 0A to a stationary supply pipe OB. The latterpreferably supplies to the distribution system fuel gas and combustionair mixed in substantially the proportion required for completecombustion.

The burners C are advantageously :of the type disclosed in the priorPatent No. 2,215,081, granted September 17, 1940, on the application ofF. O. Hess,one of the applicants herein. A burner of that type ischaracterized by the introduction of the combustible mixture into itscup shaped combustion chamber, in the form of a multiplicity of finestreams or jets distributed about the burner axis and each extendingaway from the burner axis alongside an adjacent portion of thecombustion chamber wall so that the fuel and air jets burn alongside andin close proximity to the concave refractory wall or combustion chamber.The products of combustion formed eventually escape from the furnacechamber through an elongated roof slot or space A between the adjacentupper edge portions of the separable halves of the furnace structure. Asshown in Figs. 1 and 2, the combustion gases passing through the roofslot A are drawn into and through an elongated hood Q with a centraloutlet Q. The latter may be connected to a stack or other hot gasexhauster which need not be shown or described.

In the preferred form shown, each of the columns F included in the tubesupporting rack or frame D comprises a tubular metallic pipe or corepart R encased in a tubular shell formed of end to end tubular sectionsS of ceramic material. The different columns F are anchored at theirlower ends. To this end, each core or pipe part R has its lower endsection welded at its lower end to a horizontal pipe T mounted in andsecured to saddle-like supports T' anchored in the substructuresupporting the track rails I. The columns F extend upward through theroof slot A in the furnace when its two halves are in their normalabutting relation, as shown in Fig. 3 and in full lines in Fig. 2. Theupper ends of the metallic pipe or core part R are welded to and openinto a horizontal pipe U. The pipes T and U serve as the supply andoutlet pipes respectively of a circulation system for passing waterupward through the pipes or metallic cores R of the columns F to keepsaid cores at a substantially constant and relatively low temperature.The pipes R are thus not only protected against injurious overheating,but kept from appreciable expansion and contraction as a result oftemperature changes. The last mentioned result is especially importantwhen the tubes E and their return bend end connections E are formed ofquartz, as they may well be for use in heating corrosive liquids andvapors. of the pipes R supports vertical rows of tube supportingbrackets at its opposite sides, there being one such bracket beneatheach of the tubes E in the tube bank. In the desirable formsillustrated, each bracket comprises refractory material supported by ametallic part welded to the pipe R, and cooled by the fluid flowingthrough the .pipe. One form of these metallic parts is included in thestructure illustrated in Figs. 1 to 7, and an alternative form isillustrated in Figs. 8, 9 and 10.

In the tube supporting arrangement shown in Figs. 1 to 7, each of thepipes R is formed w th a recess or pocket r at each tube supportinglevel which extends into but does not close the path of the coolingfluid flowing through the pipe, and is open at one side of the latter toreceive the tenon-like end portion G of a tube supporting bracket G. Inthe particular structural form shown, each recess or pocket r is in theform of a tunnel which extends diametrically through the pipe R and isopen at each end. Each tunnel 'part r has its wall in the form of atube, rectangular in cross-section, and has its ends welded to the pipeR at the margins of the openings in the opposite sides of the -pipe wallin register with the bore of the tunnel. In the particular form shown inFigs. 5, 6 and '7, each pocket part 'r is formed by welding together theedges of the flanges Each of two angle bar sections, to thereby form ashort tube of rectangular cross-section.

The tube supporting brackets G are advantageously formed of somerelatively strong ceramic material, preferably silicon carbide, which isadapted to withstand the temperatures and to support the tube load towhich it is subjected. The ceramic shell formed by the section Ssurrounding each pipe R are notched at one end of each pocket r toreceive the corresponding bracket tenon G. In the desirable constructionshown, the horizontal upper edge of the external end portion of eachbracket G is formed with a shallow groove G extending radially away fromthe corresponding tubular part R and providing a cradle-like support fora cylindrical ceramic body r g which directly engages and supports theunderside of the tube E above the corresponding bracket G.

When the body g is removed from its seat G in the corresponding bracketG, the latter is easily removed from its pocket r for replacement ifnecessary, by a similarly shaped fresh bracket part which can then bereadily inserted in the pocket. After the replacement bracket G is inplace, a cylindrical part g is inserted in its groove seat G In thepreferred construction shown, a lug r is welded to the undersurface ofthe top wall of the pocket -1- and each bracket is formed with a notch Ginto which said lug extends so that the bracket G is locked againsthorizontal movement out of the tunnel. Each bracket part G, however, isproportioned and has the underside of its tenon portion G inclined sothat when the cylindrical part g is not mounted in the bracket seat Gthe bracket may be tilted to move the top edge of the portion of thebracket tenon below the level of the underside of the lug r so that thelatter will not interfere with the movement of the tenon G into and outof the pocket r. In consequence of the moderate temperature conditionsto which they are subjected, the particular metal forming the walls ofthe pipes R and the pockets r is relatively unimportant, though there isan obvious advantage in using a metal relatively immune to the oxidizingaction of the furnace atmosphere and of the water :or other coolingfluid flowing through the pipes.

In the modification shown in Figs. 8, 9 and 10, the metallic core pipeRA of the tube rack column F differs r from the pipes R of theconstruction first described, in

the omission of the tunnel parts r, and the use in lieu of each suchpart of a small diameter elbow shaped tube ra. Each tube ra ispreferably of rectangular crosssection and is welded to thecorresponding pipe RA and extends away fromthe latter to form a tubebracket supporting member. Each member ra comprises a horizontal upperleg and a downwardly inclined lower leg. Advantageously and as shown, alower end portion ra of the lower leg of each elbow pipe m extends intoits supporting pipe RA and serves as a scoop to deflect some of the upflowing water in the pipe RA through the elbow pipe, as indicated by thearrows in Fig. 8. Each leg of each elbow tube ra is ordinarily welded tothe corresponding pipe RA at the margin of the opening formed in thelatter to receive the end of said leg.

In the form of the invention shown in Figs. 8 to 10, each ceramicbracket portion GA is in the form of a hollow lug integrally connectedto a semi-cylinder SA, which in conjunction with a second semi-cylinderSB of ceramic material forms a section of the ceramic shell enclosingthe pipe RA. Each of the tubular ceramic sections formed by part SA andassociated part SB extends from the level of the underside of a tube Ein one tube row to the level of the underside of'the tube in the otherand opposed tube row at the next higher level. The hollow interior GA ofthe ceramic bracket part GA is shaped to :receive and snugly house thecorresponding metallic tubular part ra. As shown, each ceramic part GAis formed with an opening in the top wall of the space GA to receive aremovable part GC which preferably is of rectangular prism form and isdirectly supported by the upper horizontal leg of the correspondingtubular part m. The part "it, may be formed of metal or of strongceramic material such as silicon carbide and is free to movelongitudinally of the tube E which it supports when that expands andcontracts in response to temperature changes. The described constructionof the ceramic parts GA and SB permits each such part to be separatelyreplaced in the event of its failure or impairment.

The abutting vertical edges of the ceramic shell sections SA and SB areadvantageously cemented together. The shell 5 of the construction shownin Figs. 1 to 7 may also be formed of semi-cylindrical sections havingabutting edges cemented together. in each form, the ceramic shell mayhave its inner wall formed with small grooves s forming air insulationspaces between the ceramic shell and metallic pipe core and thusreducing the amount of heat transferred from the ceramic shell to themetallic core which it surrounds.

The present invention may be used with advantage in apparatus varyingWidely in dimensions and capacity, and in heating various liquid andgaseous 'fluids to various temperatures. The invention is especiallyuseful, however, in heating a fluid to relatively high temperatures bythe transfer of heat at relatively rapid and regulated rates to thetubes through which the fluid flows. Merely by way of illustration andexample, it is noted that in one practical embodiment of the inventionin the form shown in the drawings, the tubes E in the tube bank areconnected to form a continuous flow path between its inlet and outletends E and E which is about 175 feet long, the internal diameter of thetubes being about 6 inches. The gaseous type fluid flowing through thetubes in said embodiment of the invention, is heated from an inlettemperature of about 300 F. to an outlet temperature of about 1832 F.The invention is well adapted for use, however, in units which arelarger and smaller than the one just referred to. Thus, for example, theinvention is well adapted for use in an oil refinery still in which thetube bank may be 60 feet long and 40 feet high. in such an installationthe tubes may be formed of alloy steel, and may be supported in somecases at least, on racks or by hangers in the manner thereforecustomary.

Where the conditions of operation are such as to make it necessary orpractically desirable to use the ceramic brackets G or other supportsfor the fluid heating tubes, which may require relatively frequentreplacements or repairs, there is an especial advantage in forming themain furnace structure in separable parts, each movable back and forthbetween its normal position and a second position more distant from thetube bank to provide access to the space between the tube bank and theburner walls which may be entered for inspection, repair and replacementpurposes without requiring the furnace structure to be first cooled downto atmospheric temperatures. As those skilled in the art will recognize,hydraulic or other servomotors of known type may be used to move thetrucks or platforms H and it back and forth along the track rails J.

While in accordance with the provisions of the statutes we haveillustrated and described the best forms of embodiment of our inventionnow known to us, it will be apparent to those skilled in the art thatchanges may be made in the forms of the apparatus disclosed withoutdeparting from the spirit of our invention as set forth in the appendedclaims, and that in some cases certain features of our invention may beused to advantage without a corresponding use of other features.

Having now described our invention, what we claim as new and desire tosecure by Letters Patent is:

1. A supporting structure for superposed horizontal fluid heater tubesand adapted to withstand high temperatures and comprising a verticallydisposed metallic pipe adapted to be cooled by the flow of a fluidthrough its bore and formed with horizontally extending hollow pocketshaving metallic walls which extend diametrically through the pipe in thesame direction at different levels but do not close the pipe bore, saidpockets being rigidly attached to the pipe at opposite sides thereofwhere the pocket extends through the pipe, and adjacent pockets beingopen at opposite sides of the pipe, and brackets of heat resistantmaterial each having a portion extending into and removably anchored ina corresponding one of said pockets and having a tube supporting portionexter nal to and extending away from said pipe.

2. A tube supporting structure as specified in claim 1, including aceramic shell surrounding said pipe.

3. A tube supporting structure as specified in claim 2, in which saidshell is formed in replaceable sections.

4. A supporting structure for superposed horizontal fluid heater tubesand adapted to withstand high temperatures and comprising a verticallydisposed metallic pipe adapted to be cooled by the flow of a fluidthrough its bore and formed with pockets having metallic walls andextending into the pipe at difierent levels but not closing the pipebore, and each pocket being open at one side of the pipe, and removablebrackets each having a portion extending into and removably anchored ina corresponding one of said pockets and having a tube supporting portionextending away from said pipe, each bracket being formed with a shoulderat the top of its pocket entering portion and the top wall of the pocketentered being provided with a shoulder adapted to engage the firstmentioned shoulder to prevent the bracket from being moved out of thepocket while in its normal horizontal attitude but permitting movementof the first mentioned shoulder beneath the second mentioned shoulderwhen the outer portion of said bracket is tilted upwardly relatively tothe portion inserted in said pocket.

5. A supporting structure as specified in claim 4, including a tubesupporting part removably received between the lower side of a tubesupported by a said bracket anchored in the vertically disposed pipe andthe outer portion of said bracket.

6. A supporting structure as specified in claim 4, in which end to endtubular sections of ceramic material surround said pipe and are formedwith openings in register with said pockets.

References Cited in the file of this patent UNITED STATES PATENTS539,364 Lipphard May 14, 1895 622,778 Nordyke Apr. 11, 1899 996,926Harrington July 4, 1911 1,380,570 Lehman July 7, 1921 1,622,303 Wyld etal Mar. 29, 1927 1,748,656 Saemisch Feb. 25, 1930 1,850,021 Manone et alMar. 15, 1932 2,325,945 Fuchs Aug. 3, 1943 2,513,626 Corriston July 4,1950 2,557,569 Schutt June 19, 1951 2,578,332 Williams Dec. 11, 19512,606,536 Hess et al Aug. 12, 1952 2,619,077 Schauble et a1 Nov. 25,1952 2,652,037 Lewis et al Sept. 15, 1953 FOREIGN PATENTS 353,226 GreatBritain July 23, 1931

